Many Senate Republicans began to announce opposition Thursday to a bipartisan budget agreement — even as their House counterparts passed it — actions unlikely to imperil the deal but that will make vote counters sweat in the closing days of 2013.

Most GOP senators facing primary challengers in 2014 have either declared their opposition to the framework or are expected to do so in the coming days, which perhaps creates for them the ideal political scenario: Congress puts itself on track to avoid a shutdown by setting appropriations levels for the next two years that have bipartisan support while these Republicans get to tout their conservative bona fides in breaking with the party.

“After careful review of the agreement, I believe it will do disproportionate harm to our military retirees,” said in-cycle Republican Lindsey Graham of South Carolina, in one of the first statements to buck the deal. “Our men and women in uniform have served admirably during some of our nation’s most troubling times. They deserve more from us in their retirement than this agreement provides.”

Graham's been one of the most persistent GOP critics of the effect of automatic sequester cuts on the military.

The framework brokered by House Budget Chairman Paul D. Ryan, R-Wis., and Senate Budget Chairwoman Patty Murray, D-Wash., includes cuts in both military and civilian pensions to offset some of the across-the-board spending cuts approved in 2011. The House passed the legislation 332-94. To avoid another government shutdown, however, appropriators will still need to draft an omnibus spending bill by Jan. 15 that gets approved by both chambers.

Graham was not alone in his dissent Thursday. Sens. Bob Corker, R-Tenn., and Richard C. Shelby, R-Ala., told #WGDB they would not support the bill.

"I understand that [Ryan] was in because of what happened this fall, and also I know there were appropriators that ... made it difficult," Corker said. "I voted for the Budget Control Act back in 2011."

"It's the same old thing where ...we'll go ahead and spend the money now and in years nine and ten down the road we hope someone else will not," Corker added.

Sen. Jeff Flake, R-Ariz., who is leaning against the agreement, echoed Corker's concern, calling it "kind of the age old spend now, save later."

Also against the plan are Roger Wicker of Mississippi and Kelly Ayotte of New Hampshire. They released separate statements Thursday also decrying the military pension changes.

Sen. Thad Cochran, R-Miss., who just announced that he would seek another term in 2014, said that he had not decided how to vote on the agreement, but acknowledged the announced opposition of his home-state colleague.

"I do not support paying for increased federal spending on the backs of our retired and active duty troops," Wicker said in a statement. "Congress should not change the rules in the middle of the game for those who have chosen to serve our nation in the military. We can and should do a deal without cutting the benefits of our men and women who have volunteered for a military career. The plan should be rejected."

Ayotte, like Corker, expressed concern that Congress would be locked into a two-year agreement without setting a path for structural entitlement reform. She noted in a brief interview, however, that if negotiators had to change the pay-fors on the original Murray-Ryan deal, "I certainly would look at the agreement differently and I'd take a look at it."

But Sen. John McCain, R-Ariz., who often agrees with Graham and Ayotte, was one of the rare GOP senators to tell reporters he was leaning toward supporting the measure, even though he would prefer that military pensions not be cut.

"It's a very serious concern, but the fact is, if we shut down the government, we hurt the military very very badly... as well as fellow citizens," McCain said, before adding that he is "leaning toward voting for it."

It's hard to see the deal achieving the 60 votes needed to invoke cloture without Republican appropriators Susan Collins of Maine and Lisa Murkowski of Alaska. Neither of the two moderates would commit when asked about the Ryan-Murray legislation as the House voted Thursday.

"Obviously, it's the details that you've got to focus in on, and that's what we're doing now in the midst of all of this jack-in-the-box we're doing," Murkowski said, in reference to the week's pop-up Senate floor votes on nominations.

"I'm in the process of reviewing it," Collins said, then adding, "I think we need a budget I am concerned about the cuts in the military."

"We need Republican votes to pass the budget agreement, period. We need at least five, and I'm hoping that there'll be more than that," Durbin said. "There are not five who Republicans have announced they're for it, I mean to my knowledge, and I hope there are many more than that and they're just holding back for any number of reasons."